Transmission for drilling machines



April 3, l951 I J. GERENTES 2,547,079

TRANSMISSION FOR DRILLING MACHINES Filed April 17, 1948 f', m m\Patented Apr. 3, 1951 TRANSMSSION FOR DRLLING MACHINES .lean Gerentes,Saint-Etienne, France, assigner to Constructions Electro-Mecaniques deSaint- Etienne, Saint-Etienne, France, a French com- Dany ApplicationApril 17, 1948, Serial No. 21,649 In France May 5, 1947 7 Claims.

The present invention relates to drilling-machines which have to boreholes in hard and heterogeneous materials, especially minerals.

The portable ele'tric drilling-machines used up to the present mine*-and quarries, are of two types. In onel the dr is fed to the work by theworkman through pushing axially on the machine; in the other, the drillis fed to the work by a step-up gear device, the machine being mountedon a head-frame.

The second type of drilling-machine mentioned above, is more suitableespecially in the case of work in hard or heterogeneous ores and forwhich a heavy feed pressure is necessary so that the drill can normallycarry out the perforating.

This feed pressure is obtained in different ways either by assembling'the drilling-machine on an arm and by feeding it to the work by screw orrack-or else by keeping the drilling-machine xed, and in making thedrill-piece move forward at the same time as the rotary motion isproduced.

With the last manner of procedure, the feed movement is given by thedriving shaft which at the same time causes the rotary motion of thedrill-piece. The feed mechanism is often friotionally-furnished, but thecharacteristic of this device is to give a fixed travel per turn,whatever be the hardness of the rocks drilled, until the elements of thefriction device Slips the one on the other or the motor stalls. Theaxial force to be applied on the drill can become considerable incertain rocks and this fact compels to increase the size andconsequently the `weight of the members of the machine-so that saidmachine becomes very uneasy to handle.

The invention has for its object to provide an electric rotarydrilling-machine, with variable automatic feed movement, light thereforeeasily handled, more particularly intended for mines and quarries.

The invention has more especially for its object to provide a drillingmachine which comprises two independent mechanisms, one for the feedmovement, and the other for the rotation of the drill-piece, thesemechanisms being driven by two separate electric motors, the motor forthe *eed movement being a motor having a high rotor slip so that thespeed of said motor varies with the hardness of the material cored andsaid mechanisms being combined so that the feed speed is a directfunction of the difference between the speeds of said motors.

Owing to these features, the feel-,1L of the drillpiece is automaticallyvariable, according to the hardness of the material bored, for saidhardness modifies automatically the speed of the corespcnding motor;said fact is very important for machines which, having to bore holeswhich may exceed a depth of two metres, meet with different strata ofmaterial of quite different hardness.

Other features of the invention will be apparent from the followingdescription.

On the accompanying drawing, given merely as an example:

Fig. i shows a longitudinal section of a drillingmachine according tothe invention;

Fig. 2 is a front view thereof;

Fig. 3 is, in section, a detail of embodiment of the nut, causing thedisplacement of the drillpiece;

Fig. l is an electric wiring diagram.

According to the example shown, the machine comprises a casing formed oftwo parts l and 2, joined through the medium of a cheek or crosspiece 3.

In the casing l is housed a main electric motor, of which the shaft 5rotates in ball-bearings 6 and l; it is provided at the back with a fan8 intended to create a current of cold air along the sides of the casingof the motor in order to cool them.

In the front, the shaft 5 extends through the cross-piece and ends inthe form of a toothed part 5l. Said toothed part 9 engages, through themedium of an idle pinion l0, with a toothed crown ll. The pinion i!! isfreely centered, on the one hand oy means of a ball-bearing lll on atrunnion ll integral with the cross-piece 3, and on the other hand bymeans of another trunnion 42 integral with said pinion l@ in aball-bearing 43 carried the part 2 of thev casing. The crown l lcomprises a hub, centred by bearings l2 and l2-- in said cross-piece 3and in a bush 2l. In this hub is keyed slidingly, according to the axisXX, a screw $3, by grooves Ita which give to this screw the rotarymovement conveyed by the gear train.

On the endv of the screw 53 is secured the drivdevioe lll of t1 edrill-piece. A housing Lia is provided inside the screw for the centringof the said drill-piece.

The longitudinal displacements of the screw i3 in the direction of thearrow fr in reverse direction, are given to independently of the abovedescribed mechanism which ensures its rotation, by the followingmechanism.

In the casing 2 is placed a Second electric auxiliary motor l5. t isconstituted by a reversible motor of a well known type enabling a highrotor slip, that is to say, a motor in which the rotary speed of therotor can decrease in very big proportions when the resisting torqueincreases. This motor may be for instance an asynchron motor having aparticularly solid squirrel-cage rotor. The shaft it of said motorrotates in the casing 2 and in a cover Il secured to this casing,drives, through the medium of a pinion it keyed on it, and of anintermediary idle pinion lil centered on the trunnion ft2, a toothedcrown 26. This crown is keyed on the bushing 2l. rlhis bushing,concentric to the screw i3, is centered by the ball-bearings 22 and 23in the casing 2. These bearings are locked longitudinally by a nut 24.

In the bushing 2l is mounted a nut 25 driven by lugs 2li (Fig. 3)engaging in the notches of the said bushing 2l; this nut is locked onthe bushing by a check-nut Eea. 'In this nut 2li is screwed the screwi3.

Fig. 4 shows the electric devices and their connections in the case offeeding by alternating current.

The current collector 2t is a live-plugged one 2e, corresponding tothree feeding leads 3Q and to two `pilot leads 3l serving to control therelays which open or cut olf the main current (usual relays, not shown,placed in a cabinet apart from the drilling-machine). A control switch32 placed in the circuit of these leads 3i therefore allows the puttingunder tension or out of tension of the main leads Sii.

The main motor i driving in rotation the Vscrew i3, is connecteddirectly to the three leads 3e.

On the contrary, the feeding motor l is connected to the three leads 3i?by a reversible switch of a conventional type with twin keys 33 andcontact-studs 3d and 35. In a certain position (keys 33 on thecontact-studs 3d for example), the motor l5 turns in the same directionas the main motor and this corresponds to .the feeding movement of thetool in the direction of the arrow f1; in another position, the motor l5turns in the reverse direction to the main motor and this corresponds tothe backward return of the tool.

The machine operates as follows: by closing the control switch 32, thelead Sil is put under tension. The main motor fl, fed, drives in rotarymotion the screw i3 through the gear trains il, i, Il and as a result,the drill-piece.

By closing the switch twin keys 33 on the contact-studs 34, theauxiliary motor i5 is fed so that this motor l5 turns in the samedirection .as the motor il. The nut is therefore driven in rotationaround the axis XX in the same direction as the screw le, and this at ahigher speed than that of the screw, the ratio of the train I8, I9, 2@being lower than the ratio of the train El, il), i I. The screw i3therefore undergoes towards the front a longitudinal displacement whosevalue depends on the difference between the speeds of the nut and of thescrew.

progressively with the feed movement of the drill-piece in the directionof the arrow f1, if the Ymaterials met with have a variable hardness,there results a corresponding variation of the resistance to the feedingmovements and an increase of the resisting torque on the motor l5. Thismotor, by reason of its high-rotor slip coeicient, slows up, and it isthe same with the lfeeding movement which finds itself stopped when thenut turns at the same speed as the screw. The feeding thus remainsconstantly proportional to the difficulty of boring. The pressure on thedrill-piece is therefore adjusted automatically, according to thehardness of the rock.

By reversing the switch twin keys 32 on the contact-studs 35, the rotarydirection of the auxiliary motor is changed and, as then no resistanceis offered to the displacement towards the rear of the screw iii, themotor turns at its highest speed, and there is obtained, by addition ofthe reverse speeds of the screw i3 and the nut 25, a very quick returnaxial travel of the drill-piece.

lt is advisable to note, moreover, that the arrangement described, inwhich the members situated around the screw it forming a pilingupbetween the ball-bearingi2 and the nut iii, permits an easy and veryquick dismantling and assembly of the different devices.

The nut 25 is easily interchangeable through simply unscrewing thecheck-nut 2da; this allows an easy adapting of the machine according tothe nature of the ground or other heterogeneous material to be drilled,by replacement of the nut 25 and the screw I3 by another set having adifferent thread.

The invention is natu-rally not limited to the embodiment shown anddescribed, which has been chosen merely as an example.

Having now described my invention what I claim as new and desire tosecure by Letters Patent is:

l. In an electric drilling machine a casing, a screw-threaded shaftprojecting at least by one of its ends from said casing in the walls ofwhich it is mounted so as to be able to rotate around and to slide alongits own axis, a tool-holder carried by said end outside said casing, afirst .electro-mechanical driving device located in said casing andcomprising a gear member rotatably mounted in said casing and in whichsaid shaft is slidingly keyed and. an electric motor secured in saidcasing for imparting to said gear member a rotation and a secondelectro-mechanical. driving device located inside said casing andcomprising a nut which is rotatably mounted in said casing so as to beunable to move longitudinally and in which said shaft is screwed and anauxiliary motor having a high rotor slip for driving positively saidnut, so that the feeding axial speed and the return axial speed of saidshaft are direct functions of the difference between the speeds ofrotation imparted by said motors respectively to said shaft and to saidnut.

2. An electric drilling machine according t0 claim l wherein saidauxiliary motor is a reversible motor and is combined with a controlswitch disposed in its feeding circuit.

3. An electric drilling machine according to claim 1 wherein said firstelectro-mechanical driving device comprises said main motor, a pinionsecured on the shaft of said motor, an idle intermediate pinion mountedin said casing to rotate freely around its axis which is stationary andsaid gear member in which the screw shaft is slidingly keyed, said idlepinion meshing with said pinion secured on the shaft of said motor andwith said gear member.

4. An electric drilling machine according to claim l wherein said secondelectro-mechanical driving device comprises between said auxiliaryelectric motor and said nut a gear transmission comprising a pinionsecured on the shaft of said auxiliary motor, an intermediate idlepinion mounted in said casing to rotate freely around its axis which isstationary and a toothed bushing rotatably mounted in said casing and inwhich is keyed said nut, said intermediate idle pinion meshing with saidpinion secured on said shaft of the auxiliary motor and with saidbushing.

5. An electric drilling machine comprising in combination a casing, ascrew-threaded shaft projecting at least by one of its ends from saidcasing in the walls of which it is mounted so as to be able to rotatearound and to slide along its own axis, a tool-holder secured to saidend of said shaft, a first electro-mechanical driving device which islocated in said casing and comprises a crowned gear member rotatably7mounted in said casing and in which said shaft is slidingly keyed, amain electric motor secured to said casing and a first gear trainconnecting said motor to said crowned gear member, a secondelectromechanical driving device situated inside said casing andcomprising a toothed bushing rotatably mounted in said casing so as tobe unable to move longitudinally, a nut which is keyed in said bushingand in which said shaft is screwed, an auxiliary reversible electricmotor having a high rotor slip and a second gear train connecting saidauxiliary motor to said bushing, and a control switch placed in thefeeding circuit of said auxiliary motor.

6. An electric drilling machine according to claim 5 wherein the ratioof said rst gear train is lower than the ratio of said second gear trainand said switch is so arranged that for the feeding drive said nut turnsin the same direction as said screw-threaded shaft but quicker than it.

7. An electric drilling machine which comprises in combination a casingformed by a front wall, an intermediate wall and a rear part, assembledtogether so as to form a front compartment and a rear compartment, saidfront wall being provided with an aperture and said intermediate wallbeing provided in said front compartment with a bearing recess, a rstball-bearing centered in said bearing recess, a crowned gear memberhaving a hollow hub formed by axial projections from both faces of saidmember, one of said projections being centered in said rst ball-bearing,a screw-threaded shaft the longitudinal axis of which coincides with theaxis of said hub in which said shaft is slidingly keyed, said shaftprojecting at least by one extremity which forms a part of atool-holder, from said casing through said aperture of said front Wallof said casing in the intermediate wall and rear part of which saidshaft is mounted so as to be able to rotate around and to slide alongits own axis, a second ball-bearing centered on the other projection ofsaid hub, at least a third ball-bearing coaxial to said first and secondball-bearings and secured in said casing in said front compartment, abushing provided with outer teeth and centered on said rst and thirdball-bearings, a nut keyed in said bushing uand in which saidscrew-threaded shaft is screwed, a check-nut screwed on said bushing insaid aperture of said front wall and abutting said nut to keep saidlatter in position longitudinally with respect to said bushing, a mainelectric motor located and secured in said rear compartment, the shaftof said motor protruding into said front compartment through saidintermediate wall, a first gear transmission in said front compartmentbetween the front end of said shaft of said main motor and said crownedgear in order to rotate the screw-threaded shaft around its ownlongitudinal axis, an auxiliary reversible electric motor having a highrotor slip, located and secured in said front compartment, a secondtransmission gear between said auxiliary motor and said bushing torotate said nut, and control electric switch placed in the feedingcircuit of said auxiliary motor.

JEAN GRENTS.

REFEREN CES CITED The following references are of record in the 4le ofthis patent:

UNITED STATES PATENTS Number Name Date 1,221,391 Thullen Apr. 3, 19172,023,841 Kingsbury Dec. 10, 1935 2,333,341 Scrivener Nov. 2, 19432,434,120 Paget Jan. 6, 1948

